Method for producing lining panels which are cast into concrete as an integral lining

ABSTRACT

Large area lining panels (1) composed of thermoplastic material are used as pouring forms and linings for concrete vessels. On the face of the lining panels (1) that contacts the concrete there are arranged in rows a plurality of anchoring knobs (2) also made of thermoplastic material which have a circular or polygonal cross section with conically inclined surface portions. A plurality of the anchoring knobs (2) are simultaneously placed on the lining panel (1) and joined to it by ultrasonic, vibratory or rotational welding. The placing and welding of the anchoring knobs (2) singly or simultaneously in groups at a predetermined distance from each other is effected in a continuous succession.

TECHNICAL FIELD

This is a continuation of application Ser. No. 06/356,469 filed Mar. 9,1982 and issued as U.S. Pat. No. 4,508,581 on Apr. 2, 1985.

The present invention relates generally to a method of producing largearea thermoplastic panels having a plurality of anchoring knobs arrangedto be embedded in a poured concrete structure to be lined with thepanels. More specifically, the present invention relates to a liningpanel having a plurality of anchoring knobs where the anchoring knobsare arranged in close proximity to each other in rows on the rear of thelining panels, are composed of thermoplastic material, and preferablyhave a circular or polygonal cross-section with optionally undercut andconically inclined surface portions.

BACKGROUND ART

Thermoplastic lining panels are used as chemically resistant,water-tight and gas-tight protection for concrete structures such aslarge containers, basins, ducts, etc. They are, therefore, subjected toconsiderable static and dynamic stresses due to movement of liquid,pressure changes, stresses derived from suppressed thermal expansion,etc. Owing to the stresses thus produced in the lining panels,mechanical anchoring is necessary for producing a secure union betweenpanels and concrete. This anchoring must be such that theabove-mentioned stresses can be dissipated by a uniform distributionover the entire surface of the panel into the concrete of the structurelined with the lining panels. This results in a field of repressedstresses which is distributed uniformly over the entire area of thepanel and avoids crack-propagating peaks of stress of the type occurringwhen the union between the panel and the concrete is unevenlydistributed.

The magnitude of the stresses occurring in the lining panels also makesit virtually impossible to adhere the lining panels directly onto theconcrete. Instead, the rear of the lining panels have to be provided inknown manner (German Offenlegungsschriften Nos. 20 37 074 and 21 24 227)with a plurality of anchoring knobs which are arranged in closeproximity to each other in rows and which have a shape which is adaptedto the structural conditions, preferably a circular or polygonalcross-section with undercut inclined running surface portions. Theanchoring knobs have to be provided in sufficient numbers per unit areato ensure that the stresses between the lining panels and the concreteare distributed uniformly.

Various methods of joining these anchoring knobs to the lining panelsare known.

In one method (German Offenlegungsschrift No. 21 24 227), large arealining panels composed of thermoplastic materials, which areparticularly well suited to such lining purposes and are alsoinexpensive, are provided on their rear faces with the desired number ofanchoring knobs of a shape adapted to the structural conditions. Toensure that the union between the relatively small end faces of theknobs and the rear of the panel is able to take up the strong shearingand tensile stresses resulting from the above-mentioned stresses, theanchoring knobs, in this method, are poured or injected onto a glassfiber mat which has previously been affixed to the rear of the liningpanel. The liquid polyester resin from which the anchoring knobs areformed penetrates deep into the fabric of the glass fiber mat as theresin is being poured or injected and, after setting, forms with the mata fracture-proof material which is firmly bonded to the rear of thelining panel.

The need to attach the glass fiber fabric beforehand and the applicationof optionally divided molds for the knobs to be poured or injected makethis method relatively complex. It is also necessary to use threedifferent materials, namely, the actual lining panel composed ofthermoplastic, the glass fiber fabric for the glass fiber mat, and theliquid plastic for the anchoring knobs. Finally, the anchoring knobs,which are formed from a liquid thermosetting resin and are no longerworkable when heated, represent an obstacle in the hot working of thelining panels into round shapes and the formation of corners, if theanchoring knobs are located in the corner region.

According to another known method (German Offenlegungsschrift No. 14 79233), the above-described necessity of using three different materialscan be avoided by producing the anchoring elements from strips ofmaterial which are pared from the rear of a plastic panel using cuttingtools and which are relatively broad in comparison with the thickness ofthe pared strip. The pared strips are bent around the root of the paredstrip still connected to the panel during paring at a steep angle to theplane of the panel. Furthermore, parallel knicks and other knicksinteresting with them are provided. However, the resultant anchoringelements are not suitable for conveying into the concrete the forcesneeded for suppressing stresses in the lining panel as, on the one hand,the root cross sections of the pared strips are too small for thispurpose and, on the other hand, the pared strips themselves are flexibleover the height needed for practical anchoring the concrete and are nottherefore resistant to bending. This design also hinders the uniformflow of the concrete needed on the surface of the panels and preventsthe air from escaping and therefore bubble-free pouring of concreteagainst the lining panels.

According to another known method (French Pat. No. 11 02 294), liningpanels can be produced from thermoplastic materials by extrusion.Anchoring strips which are formed over the length of the rear of thepanel and are optionally undercut can be provided and can be split intoknob-like portions by the milling of intermediate spaces. It has beenfound that this method is suitable only for relatively thinthermoplastic panels of 2-3 mm, but not for the panels of 4-10 mimneeded in the present method, as rejects are produced owing to theuneven flow of material during extrusion, and unavoidable hollows areformed on the side of the panel opposite the anchoring strips. Anotherdisadvantage of these extruded anchoring strips lies in the fact thatthe forces are dissipated along parallel lines and over a relativelynarrow strip-root width, which obstructs uniform flow of stress insidethe panel. If the strips are arranged in very close proximity to eachother, there is a risk of the intermediate spaces not being filled bythe conventional concrete containing coarse aggrgates and of bubblesbeing formed. However, if the strips are arranged at large distancesfrom each other, the strips will bulge apart due to expansion, forexample, under elevated thermal stresses, and this can lead to fatiquefailure during a change of temperature.

It might also be possible to inject the lining panels in one piecetogether with the anchoring knobs. However, the results of such a methodare limited to the possible size of the injection mold and theestablished shape of the anchoring knobs and to the distribution ofthese anchoring knobs. Any change would necessitate the production of anexpensive new mold. The above-mentioned disadavantages (French Pat. No.11 02 294) of the unavoidable and undesirable hollows due to the unevendistribution of mass on the surface of an extruded panel opposite theanchoring knobs would also arise with an injection molded panel.

DISCLOSURE OF INVENTION

It is, therefore, an object of the present invention to provide a methodof producing large area thermoplastic lining panels having anchoringknobs on the surface of the panels, in which the disadvantagesassociated with the known methods described above are avoided and therestrictions in use are eliminated.

The object is achieved in that anchoring knobs are placed singly orsimultaneously in groups on the lining panel and are joined to it byultrasonic, vibratory or rotational welding. The placing and welding ofthe anchoring knobs singly or in groups at predetermined distances fromeach other can be effected automatically in a continuous succession. Asalso proposed by the invention, the knob body having a circular orpolygonal cross section is provided at one end with an attachment platewhich enlarges the weld contact face on the lining panel. The knob canbe composed of a material which is identical or related to that of thelining panels.

By means of this method, it is possible to provide all shapes ofconventional commercial thermoplastic panels of differing thickness andof random dimensions with anchoring knobs of any desired shape anddistribution over the panel surface. The thermoplastic lining panel issubjected to heat only in the immediate region of contact with theanchoring knob so that there is no risk of having to reject the panelowing to the heat of welding, as would be the case if it were joined,for example, by butt welding. The distribution of stresses andtransmission of stresses takes place, independently of the selectedshape of the actual knob body, over a large area of the attachment platewhich enlarges the attachment end of the knob body and which forms theweld contact face on the lining panel.

The invention is described in more detail with reference to theembodiment illustrated in the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevation, partially in section, showing the anchoringknobs and the lining panel.

FIG. 2 is a view similar to FIG. 1 showing the lining panel in relationto a poured concrete structure.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, the anchoring knob 2 is held by a holding device 3,which is designed as an ultrasonic transducer in this case. As theholding device 3 is lowered, the anchoring knobs 2 are moved from theposition shown in solid lines into the position indicated by chain linesand are welded to the lining panel 1 by the effect of ultrasound. Theanchoring knobs 2 are supplied from a magazine in known manner, aredistributed by means of an apparatus, not shown, to a plurality ofstationary or movable holding devices 3, and are placed at variable orfixed intervals from each other on the lining panel. Changing to otherforms of anchoring knobs requires merely changing the holding devices,for example, from a device for holding a body 2a having a circular crosssection to a device for holding a body having a polygonal cross section.The anchoring knob 2 is formed at one end face 2c with an attachmentplate 2b to enlarge the weld contact face 2d on the lining panel 1,which permits welding by ultrasound, vibration, or frictional rotationand thus produces a large area of connection with the lining panel 1 inrelation to the cross section of the body 2a of the anchoring knob 2.

The anchoring knobs 2 consisting of the knob body 2a and the attachmentplate 2b can be produced in various shapes. The knob body 2a must beheld firmly in the concrete, and the attachment plate 2b must berelatively large relative to the cross section of the knob body 2a toensure that the stresses resulting from differential thermal expansionof the concrete and thermoplastic lining panel are transmitted by theembedded knobs uniformly and over a large area, as shown in FIG. 2,which illustrates the finished lining panel 1 provided with anchoringknobs 2 embedded in a cast concrete body 6.

I claim:
 1. A method of producing large area lining panels for pouredconcrete structures, the method comprising the steps of:providing asheet-like panel composed of thermo-plastic material, each panel havinga front face and a rear face; providing a plurality of anchoring knobscomposed of thermoplastic material, each anchoring knob having a bodywith a first end and a second end and an attachment portion integrallyformed at the first end of the body; placing the contact surface of theattachment portion of each anchoring knob in contact with the rear faceof the panel in predetermined spaced relation to other ones of theplurality of knobs; and effecting frictional heating of the immediateregion of contact between each anchoring knob and the panel sufficientto fuse the contact surface of the knob and the contacted surface of thepanel to weld the anchoring knobs to the panel, whereby each knob isadapted to distribute shear and tension forces to the panel when theknob is embedded in a poured concrete structure abutting the rear faceof the panel.
 2. A method according to claim 1 wherein said step ofeffecting frictional heating of the immediate region of contact betweeneach knob and the rear face of the panel comprises applying vibrationalenergy to the body of the knob.
 3. A method according to claim 1 whereinsaid step of effecting frictional heating of the immediate region ofcontact between each knob and the rear face of the panel comprisesapplying ultrasonic energy to the body of the knob.
 4. A methodaccording to claim 3, the method including the step of holding the bodyof each anchoring knob in a transducer device upon placing the anchoringknobs in contact with the panel.
 5. A method according to claim 1wherein said step of effecting frictional heating of the immediateregion of contact between each knob and the rear face of the panelcomprises rotating the knob while the contacting surface is in contactwith the rear face of the panel.
 6. A method according to claim 1wherein the steps of placing the knobs on the panel and effectingfrictional heating of the immediate region of contact between each knoband the rear face of the panel are accomplished automatically incontinuous succession.
 7. A method according to claim 1 wherein thematerial of the knobs is identical to the material of the panel.